Oculomotor behavior of hemianopic chronic stroke patients in a driving simulator is modulated by vision training

Abstract

Background: Visual Restorative function training aims to decrease visual field defect size after acquired brain damage. Some chronic stroke patients regain permission to drive a car after training. This points to a concomitant change in oculomotor behavior, because visual field enlargement is hardly ever large enough for legal driving. This study investigated vRFT-induced changes in oculomotor behavior, using a driving simulator. Methods: Driving performance and oculomotor behavior were measured before and after training in 6 hemianopia patients who had trained 65 hours with vRFT on a PC at home. Results: Two patients showed negligible visual field enlargement (VFE) and four showed moderate to substantial VFE. Because less visual cortex is devoted to the processing of peripheral than central visual field the same VFE corresponds to less functional restoration of cortex when the defect is at high eccentricity. When this is taken into account, then precisely the two patients that showed the largest cortical gains made significantly more eye movements in the direction of their visual field defect after training. Conclusions: vRFT with mandatory eye fixation can result in increased eye movement behavior towards the defect. Our study suggests that a threshold amount of cortical functional restoration is required for this effect.